WO2006071009A1

WO2006071009A1 - Fuel injection pump having cavitation damage-prevention structure

Info

Publication number: WO2006071009A1
Application number: PCT/KR2005/004192
Authority: WO
Inventors: Dong-Hun Kim; Sang-Hak Ghal; Ji-Soo Ha; Ju-Tae Kim
Original assignee: Hyundai Heavy Industries Co., Ltd.
Priority date: 2004-12-27
Filing date: 2005-12-08
Publication date: 2006-07-06
Also published as: CH706191B1; DE112005003302B4; FI20077126A; JP2008525704A; DE112005003302T5; FI122810B

Abstract

Disclosed herein is a fuel injection pump having cavitation damage -prevention structure, in which the structure and shape of a deflector (110) and a spill port (120) are improved, thus preventing the spill port and plunger (130) from being damaged due to cavitation. To achieve the above-mentioned purpose, the fuel injection pump of the present invention includes a means for preventing propagation of pressure waves. The propagation preventing means is provided on at least one of the spill port (120) and the deflector (110) such that pressure waves, which are generated when a jet-type cavitation, occurring just after the spill port (120) is opened strikes the spill port (120) or the deflector (110), are prevented from being propagated to cavities that remain around a side surface of the plunger (130).

Description

FUEL INJECTION PUMP HAVING CAVITATION DAMAGE- PREVENTION STRUCTURE

Technical Field

[1] The present invention relates, in general, to fuel injection pumps which compress fuel at high pressure and supply it to injectors so as to operate direct injection-type internal combustion engines and, more particularly, to a fuel injection pump having an improved cavitation damage-prevention structure to solve a problem in which elements of the pump are damaged by cavitation, a problem which has increased due to a trend of increasing fuel injection pressure.

[2]

Background Art

[3] As well known to those skilled in the art, an internal combustion engine means a mechanical machine which converts thermal energy, generated by mixing and burning fuel and air drawn into the machine, into mechanical energy. Meanwhile, diesel engines are classified into a direct injection type engine, a pre-combustion chamber type engine, a swirl chamber type engine and an air chamber type engine, according to fuel supply method. The direct injection-type engine uses a method in which fuel is directly injected into a combustion chamber, and includes a fuel pump, a fuel valve (an injector) and a connecting pipe. Furthermore, there is a unit injector in which a fuel injection pump and an injector are combined with each other.

[4] The fuel injection pump is a device which compresses fuel at high pressure and supplies it to an injector. Recently, to enhance combustion performance and reduce exhaust gas, fuel injection pressure is trending upward. Hence, problems of cavitation erosion damage to the spill port of the barrel and plunger constituting the fuel injection pump have been on the increase. Even when fuel is injected at relatively low pressure, cavitation is caused. In this case, because the intensity of cavitation is weak, the degree of damage is not serious, and only incidental damage is caused. Therefore, this problem can be easily solved by improving design or changing the material of the elements based on experience with various types of damage. However, as fuel injection pressure has been increased, the intensity of cavitation has been increased, so that complex damage to the spill port of the barrel and plunger has been caused. As well, the degree of damage has been serious. However, efforts for preventing damage to elements due to cavitation have been made merely using methods such as design revision or material change, depending on experience, without investigating the correct cause of damage. [5] As an example, a fuel injection pump, in which an orifice member is provided in each of cut-off holes formed in a sidewall of a barrel such that relatively high pressure is applied to a space defined between the orifice members and the plunger in order to prevent cavitation from occurring at a portion adjacent to an upper end of the plunger, was proposed in Korean Patent Laid-open Publication No. 2001-0020139. Furthermore, in Japan Patent Laid-open Publication No. Heisei. 7-269442, on the presumption that damage to a plunger is caused depending on the relationship between a stream current and the shape of a fuel discharge hole, a cavitation prevention mechanism for fuel injection pumps, in which a cavity breaking hole is formed adjacent to the fuel discharge hole of a barrel so as to prevent the plunger from being damaged, was proposed. As well, a spill deflector for internal combustion engines was proposed in Japan Patent Laid-open Publication No. Heisei. 7-54735. In this art, it was presumed that cavities are created just before a spill port is closed in a fuel-intake process and, thereafter, pressure waves, generated when fuel discharged through the spill port strikes a deflector, impacts the remaining cavities, so that damage due to cavitation is caused. Thus, a receptive port, which is opened or closed depending on the pressure of discharged fuel, is formed in an end of a deflector, such that fuel flowing through the receptive port is distributed outside of the barrel. In addition, a fuel injection device for internal combustion engines was proposed in Japan Patent Laid-open Publication No. Heisei. 5-340322. In this art, the cause of damage due to cavitation was not clarified, but on the assumption that damage is caused by cavities that remain around a barrel port, a protective member, with a fuel supply hole having a certain shape is provided such that cavities cannot remain around the barrel port, so that spilled fuel contacts the inner surface of the fuel supply hole of the protective member at a slanted angle.

[6] As such, various design improvement methods were proposed to solve the complex problems of cavitation damage to the spill port of the barrel and plunger due to high fuel injection pressure. However, because these methods merely depend on experience with various kinds of damage, without clarification of the cause of damage, there is a problem of no definitive measures.

[7]

Disclosure of Invention Technical Problem

[8] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a fuel injection pump having cavitation damage-prevention structure, in which the structure and shape of a deflector and a spill port are improved based on a correct un- derstanding of a cause of cavitation damage to the fuel injection pump, thus preventing the spill port and plunger from being damaged.

[9]

Technical Solution

[10] In order to accomplish the above object, the present invention provides a fuel injection pump having a cavitation damage-prevention structure and provided in a direct injection-type internal combustion engine. The fuel injection pump comprises a propagation preventing means which is provided on at least one of a spill port and a deflector such that pressure waves, which are generated when a jet-type cavitation occurring just after the spill port is opened strikes the spill port or the deflector, are prevented from being propagated to cavities that remain around a side surface of a plunger.

[H]

[12] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Detailed explanation of well-known functions and constructions will be omitted to more clearly describe the present invention.

[13] FIGS. 1 through 4 illustrate cavitations occurring according to the operation of a fuel injection pump. Referring FIGS. 1 through 4, in the case of a jet-type cavitation 30 and a waterfall-type cavitation 40 which occur at an early stage of a compression process of the fuel injection pump, because the intensity and amount of generation of the cavitation are weak due to relatively low pressure, these are insignificant. However, in the case of a fountain-like cavitation 10, which occurs until just before a spill port of the fuel injection pump is opened, because a fuel injection pressure is relatively high, a large quantity of cavities is generated around a side surface of a plunger. The generated cavities remain around the surface of the plunger. Meanwhile, in the case of a jet- type cavitation 20, which occurs at the moment the spill port of the fuel injection pump is opened, because it occurs at the moment the fuel injection pressure is at its maximum, the intensity of the cavitation is very high, and the flow speed thereof is very fast. Therefore, this cavitation causes direct damage to the spill port and, as well, a rapid increase in pressure is induced at the moment the cavitation flow strikes the spill port. It has been confirmed that such an increase in pressure causes collapse of cavities, which have been generated by the fountain-like cavitation around the plunger, and thereby the plunger is damaged. Hence, the object of the present invention is to improve the structures of the spill port and a deflector so as to prevent pressure waves generated when a jet-type cavitation, which occurs just after the spill port is opened, strikes the spill port, from being propagated to cavities around the plunger and also prevent the spill port from being directly damaged by the jet-type cavitation.

[14]

[15] First embodiment

[16] FIG. 5 is a sectional view illustrating the construction of a fuel injection pump, according to a first embodiment of the present invention. Referring to FIG. 5, the fuel injection pump according to the first embodiment of the present invention is characterized by an improved structure of a deflector 110, which is provided to prevent a barrel 100 from being damaged due to residual fuel discharged to a spill port 120 at a high speed and high pressure just after an effective stroke of the fuel injection pump. The fuel injection pump having the above-mentioned characteristics prevents a jet- type cavitation 20, which occurs just after an effective stroke of the fuel injection pump, from directly striking the spill port 120. As well, the fuel injection pump is constructed such that pressure waves generated when the cavitation strikes the spill port are prevented from being propagated to cavities around a plunger 130.

[17] FIG. 6 is a view illustrating in detail the structure of the deflector 110. Referring to

FIG. 6, the deflector 110 includes an extension part 111 and a reflective surface 112. The extension part 111 extends from an end of the deflector 110, such that it is placed in the spill port 120. Furthermore, the extension part 111 has a diameter smaller than the diameter of the deflector 110. The reflective surface 112 is planar and provided under a lower side of an end of the extension part 111, so that jet- type cavitation 20, which occurs just after the spill port 120 is opened, strikes the reflective surface 112.

[18] Meanwhile, in the present invention, the direction in which the jet- type cavitation

20 flows is changed depending on the depth (X) and length (Y) of a stepped portion of an outflow recess 131, which is formed in a side surface of the plunger 130 and communicates with the spill port 120 after an effective stroke of the fuel injection pump, such that residual fuel is discharged. Therefore, according to the depth (X) and the length (Y) of the stepped portion of the outflow recess of the plunger 130, the diameter (Dl) and installation location (Ll) of the extension part 111, the machining depth (dl) at which the reflective surface 112 is formed, and the length (11) of the reflective surface 112 are all determined. Furthermore, their precise dimensions are determined through tests or simulations using a computer.

[19] In particular, the installation location (Ll) of the extension part 111 must be determined such that the extension part 111 is placed at a position sufficiently near the plunger 130 so as to prevent the jet- type cavitation 20 from striking a front surface or upper surface of the extension part 111. Furthermore, the machining depth (dl) at which the reflective surface 112 is formed is 1/2 of the diameter (Dl) of the extension part 111 from the lowermost surface of the extension part 111 or less, such that the re- placement lifetime of the deflector 110 is not too short.

[20] FIG. 7 illustrates reflection of pressure waves by the deflector 110 having the improved structure described above. Referring to FIG. 7, a fountain-like cavitation 10, which occurs just before the spill port 120 is opened, forms a large quantity of cavities around an upper end of the side surface of the plunger 130 due to a relatively high fuel injection pressure.

[21] Furthermore, because the fuel injection pressure of the fuel injection pump reaches the maximum value just after the spill port 120 is opened, a jet-type cavitation 20 occurs and strikes the reflective surface 112 of the deflector 110 of the pump at a high speed and high pressure. As such, the jet-type cavitation 20 strikes the reflective surface 112 but does not directly strike a side surface of the spill port 120, so that the side surface of the spill port 120 is prevented from being damaged. Furthermore, most of pressure waves 20a generated when the jet-type cavitation 20 strikes the reflective surface 112 are reflected in a direction in which fuel flows, and are thus prevented from being propagated to the plunger 130. The remaining pressure waves 20b, which are reflected towards the plunger 130, are propagated to a lower portion of the side surface of the plunger 130 in which a small quantity of cavities has been generated. Therefore, erosion damage to the plunger 130 due to collapse of cavities is reduced.

[22]

[23] Second embodiment

[24] FIG. 8 is a sectional view showing the construction of a fuel injection pump according to a second embodiment of the present invention. Referring to FIG. 8, the fuel injection pump according to the second embodiment of the present invention is characterized by an improved shape of a spill port 210, which is defined in a barrel 200 to discharge residual fuel after an effective stroke of the fuel injection pump. The fuel injection pump having the above-mentioned characteristics is constructed such that, thanks to the increased distance from the position at which a jet- type cavitation 20 occurs just after an effective stroke of the fuel injection pump, to a position at which the jet-type cavitation strikes a side surface of the spill port 210, the intensity of cavitation is weakened and, as well, the pressure waves are prevented from being propagated to a plunger 220.

[25] FIG. 9 shows in detail the shape of the spill port 210. Referring to FIG. 9, the spill port 210 is configured in a shape in which an enlarged part 211 is defined at an outlet side of the spill port 210. The enlarged part 211 has an inner diameter (D2) larger than the diameter (d2) of an inlet side of the spill port 210 and is defined from the outlet side of the spill port 210 to a predetermined depth.

[26] Meanwhile, in this embodiment, the direction in which the jet-type cavitation 20 flows is changed depending on the depth (X) and length (Y) of a stepped portion of an outflow recess 221, which is formed in a side surface of the plunger 220 and communicates with the spill port 210 after an effective stroke of the fuel injection pump such that residual fuel is discharged. Therefore, according to the depth (X) and the length (Y) of the stepped portion of the outflow recess 221 of the plunger 220, the formation location (L2) and the inner diameter (D2) of the enlarged part 211 are determined. Furthermore, their precise dimensions are determined through tests or simulations using a computer.

[27] In particular, the formation location (L2) of the enlarged part 211 must be determined such that the enlarged part 211 is adjacent to the plunger 220 to prevent a jet-type cavitation 20 from striking a portion of the side surface of the spill port 210 other than the enlarged part 211. Furthermore, it is preferably designed such that the inner diameter (D2) of the enlarged part 211 is 1.5 times or greater than the inner diameter (d2) of the inlet side of the spill port 210, in order to efficiently prevent the side surface of the spill port 210 and the plunger 220 from being damaged by the cavitation erosion

[28] FIG. 10 illustrates the propagation of pressure waves changed by the spill port 210 having the improved shape. Referring to FIG. 10, a fountain-like cavitation 10, which occurs just before the spill port 210 is opened, forms a large quantity of cavities around an upper end of the side surface of the plunger 220 due to a relatively high fuel injection pressure.

[29] Furthermore, because the fuel injection pressure of the fuel injection pump reaches the maximum value just after the spill port 210 is opened, a jet-type cavitation 20 occurs and strikes the side surface of the enlarged part 211 of the spill port 210 at a high speed and high pressure. Here, thanks to the increased distance from the position at which the jet-type cavitation 20 occurs to the position at which the jet-type cavitation strikes the side surface of the enlarged part 211, the striking intensity of the cavitation is weakened. Furthermore, most of pressure waves 20a are reflected in a direction in which fuel flows. The remaining pressure waves 20b, which are reflected towards the plunger 220, are interrupted by an end wall 212 of the enlarged part 211, which is formed by a diameter difference between the enlarged part 211 and the inlet side of the spill port 210. Thus, the plunger 220 is prevented from being damaged due to collapse of cavities, generated around the plunger 220.

[30]

[31] Third embodiment

[32] FIG. 11 is a sectional view illustrating the construction of a fuel injection pump according to a third embodiment of the present invention. Referring to FIG. 11, the f uel injection pump according to the third embodiment of the present invention is characterized by an improved structure of a deflector 310 and a spill port 320. The fuel injection pump having the above-mentioned characteristics is constructed such that a jet-type cavitation 20, which occurs just after an effective stroke of the fuel injection pump, passes through a space defined between the deflector 310 and a side surface of the spill port 320, and, even if pressure waves are generated by the jet-type cavitation 20 striking the deflector, the pressure waves are prevented from being propagated to a plunger 330.

[33] FIG. 12 shows in detail the structure of the deflector 310 and the spill port 320.

Referring to FIG. 12, the deflector 310 includes a first tapered part 311, and the side surface of the spill port 320 includes a second tapered part 321 which corresponds to the first tapered part 311. The first tapered part 311 is provided at an end part of the deflector 310 by reducing in a diameter thereof to a distal end. The second tapered part 321 is formed at an outlet side of the spill port 320 such that it is tapered at an angle co rresponding to the first tapered part 311.

[34] Meanwhile, in this embodiment, the direction in which the jet-type cavitation flows is changed depending on the depth (X) and length (Y) of a stepped portion of an outflow recess 321, which is formed in a side surface of the plunger 330 and communicates with the spill port 320 after an effective stroke of the fuel injection pump, such that residual fuel is discharged. Therefore, according to the depth (X) and the length (Y) of the stepped portion of the outflow recess 331 formed in the side surface of the plunger 330, the installation location (L3), the diameter (D3) and the cone angle (α) of the first tapered part 331, and the formation location (13) and the taper angle (β) of the second tapered part 321 are determined. Furthermore, their precise dimensions are determined through tests or simulations using a computer.

[35] In particular, the cone angle (α) of the first tapered part 331 is preferably designed within an angular range from 60° to 120°, such that pressure waves, which are generated when the jet-type cavitation 20 strikes the first tapered part, are not reflected towards the plunger 330, thereby efficiently preventing the plunger 330 from being damaged by the cavitation.

[36] FIG. 13 is a view illustrating the propagation of pressure waves changed by the deflector 310 and the spill port 320 having the improved structure and shape. Referring to FIG. 13, a fountain-like cavitation 10, which occurs just before the spill port 320 is opened, forms a large quantity of cavities around an upper end of the side surface of the plunger 330 due to a relatively high fuel injection pressure.

[37] Furthermore, because the fuel injection pressure of the pump reaches the maximum value just after the spill port 320 is opened, a jet- type cavitation 20 of a high speed and high pressure occurs. Here, the jet-type cavitation 20 passes through the space between the first and second tapered parts 311 and 321 or, alternatively, some strikes the first tapered part 311. At this time, pressure waves 20a and 20b, which are generated when some jet- type cavitation 20 strikes the first tapered part 311, are reflected into the space defined between the first and second tapered parts 311 and 321 and thus does not affect cavities which are formed around the plunger 330, thereby preventing the plunger 330 from being damaged due to collapse of cavities.

[38] Although the preferred embodiment of the present invention has been disclosed for illustrative purposes, the present invention is not limited to the preferred embodiment. Furthermore, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims, and these modifications, additions and substitutions fall within the bounds of the present invention.

[39]

Advantageous Effects

[40] As described above, the present invention provides a fuel injection pump for direct injection-type internal combustion engines in which the structure and shape of the deflector and spill port of the fuel injection pump are improved based on a correct understanding of the cause of cavitation damage to the fuel injection pump, thus preventing the spill port of a barrel and plunger in the fuel injection pump from being damaged due to cavitation phenomena.

[41]

Brief Description of the Drawings

[42] FIG. 1 illustrates a jet-type cavitation which occurs at an early stage of a compression process of a fuel injection pump;

[43] FIG. 2 illustrates a waterfall-type cavitation which occurs at the early stage of the compression process of the fuel injection pump;

[44] FIG. 3 illustrates a fountain-like cavitation which occurs until just before a spill port of the fuel injection pump is opened;

[45] FIG. 4 illustrates a jet-type cavitation which occurs at the moment the spill port of the fuel injection pump is opened;

[46] FIG. 5 is a sectional view showing the construction of a fuel injection pump according to a first embodiment of the present invention;

[47] FIG. 6 is a detailed view showing the structure of a deflector shown in FIG. 5;

[48] FIG. 7 illustrates reflection of pressure waves by the deflector shown in FIG. 5;

[49] FIG. 8 is a sectional view showing the construction of a fuel injection pump, according to a second embodiment of the present invention;

[50] FIG. 9 is a detailed view showing the shape of a spill port shown in FIG. 8;

[51] FIG. 10 illustrates a reflection of pressure waves by the side surface the spill port of the fuel injection pump shown in FIG. 8; [52] FIG. 11 is a sectional view showing the construction of a fuel injection pump according to a third embodiment of the present invention; [53] FIG. 12 is a detailed view showing the structure of a deflector and a spill port of the fuel injection pump shown in FIG. 11; and [54] FIG. 13 is a view showing reflection of pressure waves both by the deflector and the spill port of the fuel injection pump shown in FIG. 11. [55]

[56] <Description of the elements in the drawing>

[57] 100 : barrel 110 : deflector

[58] 111 : extension part 112 : reflective surface

[59] 120 : spill port 130 : plunger

[60] 200 : barrel 210 : spill port

[61] 211 : enlarged part 220 : plunger

[62] 300 : barrel 310 : deflector

[63] 311 : first tapered part 320 : spill port

[64] 321 : second tapered part 330 : plunger

[65]

Claims

[1] A fuel injection pump having a cavitation damage-prevention structure and provided in a direct injection-type internal combustion engine, the fuel injection pump comprising: means for preventing propagation of pressure waves, the propagation preventing means being provided on at least one of a spill port and a deflector such that pressure waves, which are generated when a jet-type cavitation occurring just after the spill port is opened strikes the spill port or the deflector, are prevented from being propagated to cavities that remain around a side surface of a plunger.

[2] The fuel injection pump according to claim 1, wherein the propagation preventing means comprises: an extension part extending from an end of the deflector to a predetermined position in the spill port, the extension part having a diameter smaller than a diameter of the deflector; and a planar reflective surface provided under a lower side of an end of the extension part, so that the jet-type cavitation, which occurs just after the spill port is opened, strikes the reflective surface, thus preventing pressure waves generated by the strike event from being propagated to cavities that remain around the plunger and also preventing the spill port from being directly damaged by the jet- type cavitation.

[3] The fuel injection pump according to claim 2, wherein the reflective surface is formed at a depth of 1/2 of the diameter of the extension part or less from a lowermost side of the extension.

[4] The fuel injection pump according to claim 1, wherein the transmission preventing means comprises: an enlarged part having an inner diameter larger than an inner diameter of an inlet side of the spill port and provided in an outlet side of the spill port, so that the intensity of cavitaton is weakened and pressure waves, which are generated when the jet-type cavitation occurring just after the spill port is opened strikes a side surface of the enlarged part, are interrupted by an end surface of the enlarged part, thus preventing the pressure waves from being propagated to cavities that remain around the side surface of the plunger.

[5] The fuel injection pump according to claim 4, wherein the inner diameter of the enlarged part is at least 1.5 times the inner diameter of the inlet side of the spill port.

[6] The fuel injection pump according to claim 1, wherein the transmission preventing means comprises: a first tapered part provided at an end part of the deflector by reducing in a diameter thereof to a distal end; and a second tapered part formed in an outlet side of the spill port and tapered at an angle corresponding to the first tapered part, so that the jet-type cavitation, occurring just after the spill port is opened, passes through a space defined between the first and second tapered part, or strikes the first tapered part, thus pressure waves, which are generated by the strike event, are prevented from being propagated to cavities that remain around the side surface of the plunger. [7] The fuel injection pump according to claim 6, wherein the first tapered part has a cone angle ranging from 60° to 120°, such that the pressure waves, which are generated when the jet-type cavitation strikes the first tapered part, are prevented from being reflected towards the plunger.